1. Field of the Invention
This invention is related to electrically controlled propellants.
2. General Background
For a number of applications, it is desirable to control the ignition, burn rate, and extinguishment of a propellant by the application of an electrical current. For instance, orbital attitude control rockets typically fire in short, controlled bursts to incrementally adjust the satellite's position. In these instances, an electrically controlled propellant may very precisely control the duration and burn rate of the rocket.
In the past, Teflon and other substances have been used as electrically controlled propellants, but these propellants suffer from two significant drawbacks. First, they often do not extinguish as quickly as desired after the electrical current has stopped. Hence precision and accuracy of the burn and therefore of the rocket is diminished. Second, these propellants provide none of their own energy, since all the energy for propellant gas generation comes from the electrical energy source.
Therefore, a new electrically controlled propellant has been developed, as described in U.S. patent application Ser. No. 10/136,786 and 10/423,072, the disclosure of which is incorporated herein as if set out in full. The electrically controlled propellant in the '786 and the '072 patents comprise an ionomeric oxidizer binder, an oxidizer mix including at least one oxidizer salt and at least one eutectic material that maintains the mix in a liquid form at the processing temperature and a mobile phase which may include at least one polar protic high boiling organic liquid.
The '786 and '072 electrically controlled propellants require the application of electrical voltage to initiate and sustain combustion, but the energy released is potentially much greater than the energy supplied. Using the combustion exhaust it may be possible to generate sufficient electrical energy by magnetohydrodynamics (magnetofluiddynamics or hydromagnetic) to sustain and control combustion once the propellant is ignited. Such a propellant system could also find useful application for “on demand” reusable gas generators and a controllable gas generator for automobile air bags.
However, the electrically controlled propellant disclosed in the '786 patent has drawbacks of its own. Under certain circumstances it can melt or soften during combustion, thereby decreasing its effectiveness. More particularly, melting can undermine the ability of the propellant to be used in situations where the propellant must be ignited and extinguished multiple times. In addition, the fluid phase of the propellants in this application has sufficient volatility to slowly evaporate from the surface of the propellant, making its application not suitable for use in the vacuum of space.